High-efficiency reflective liquid crystal display

• US 6,317,189 B1
• Filed: 12/29/1998
• Issued: 11/13/2001
• Est. Priority Date: 12/29/1998
• Status: Expired due to Term

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Silverstein, Louis D., Yuan, Haiji, Fiske, Thomas G.
• Primary Examiner(s): Parker, Kenneth
• Assistant Examiner(s): QI, ZHI QIANG
• Application Number:
  US09/221,599
• Time in Patent Office: 1,050 Days
• Field of Search: 349/176, 349/175, 349/115, 349/113, 349/86, 349/88, 349/74, 349/78, 349/80
• US Class Current: 349/176
• CPC Class Codes: G02F 1/13342 Holographic polymer dispersed liquid crystals
• CPC Class Codes: G02F 1/13478 based on selective reflection
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal
• CPC Class Codes: G02F 2203/34 Colour display without the use of colour mosaic filters
• CPC Class Codes: G09G 2300/0486 Cholesteric liquid crystals, including chiral-nematic liquid crystals, with transitions between focal conic, planar, and homeotropic states

Abstract

A reflective display comprises a pair of substrates and a holographic polymer dispersed cholesteric liquid crystal (HPDCLC) material formed between the substrates. The holographic polymer dispersed cholesteric liquid crystal material comprises a holographic polymer dispersed liquid crystal material and a cholesteric liquid crystal material. These two materials reflect one or more different intrinsic colors such that individual cells of the display can reflect one or more different intrinsic colors. The cells can comprise more than two layers, with each layer being reflective of a different intrinsic color. The cells in such embodiments can reflect three different intrinsic peak wavelengths and one or more intrinsic colors, enabling the display to reflect all colors.

Claims

1. A reflective display, comprising:

a first substrate;

a second substrate; and

a light reflective medium formed between the first and second substrates, the light reflective medium reflects light at two or more intrinsic peak wavelengths, wherein the light reflective medium comprising a holographic polymer dispersed cholesteric liquid crystal material formed between the first and second substrates, the holographic polymer dispersed cholesteric liquid crystal material including;

polymer layers; and

cholesteric liquid crystal layers comprising a cholesteric liquid crystal material; and

the holographic polymer dispersed cholesteric liquid crystal material reflects light at a first intrinsic peak wavelength and at a second intrinsic peak wavelength.

2. The reflective display of claim 1, further comprising a voltage source that selectively applies a voltage to the first and second substrates, wherein:

when the voltage is zero, the cholesteric liquid crystal material has a substantially planar texture and the display reflects light at the first and second intrinsic peak wavelengths;

when the voltage has a first value, the cholesteric liquid crystal material has a substantially focal conic texture and the display reflects light at the first intrinsic peak wavelength and transmits light at the second intrinsic peak wavelength; and

when the voltage has a second value greater than the first value, the cholesteric liquid crystal material has a substantially homeotropic texture and the display transmits light at the first and second intrinsic peak wavelengths.

3. The reflective display of claim 2, wherein:

the voltage applied to the first and second substrates is released from the second value to a lower value at a first rate or at a second rate;

when the voltage is released at the first rate, the texture of the cholesteric liquid crystal material transforms from the homeotropic texture to the focal conic texture, and

when the voltage is released at the second rate, the texture of the cholesteric liquid crystal material transforms from the homeotropic texture to the planar texture.

4. A method of making a reflective display, comprising:

a) providing a first substrate;

b) providing a second substrate; and

c) forming a light reflective medium between the first and second substrates, the light reflective medium, the light reflective medium reflects light of at least two intrinsic peak wavelengths, the light reflective medium comprising a holographic polymer dispersed cholesteric liquid crystal material formed between the first and second substrates, the holographic polymer dispersed cholesteric liquid crystal material includes polymer layers, and cholesteric liquid crystal layers comprising a cholesteric liquid crystal material,

wherein the holographic polymer dispersed cholesteric liquid crystal material reflects light of a first intrinsic peak wavelength and a second intrinsic peak wavelength.

5. The method of claim 4, wherein the light reflective medium comprises alternating layers that comprise the cholesteric liquid crystal and the polymer.

6. A method of making a reflective display, comprising:

a) providing a first substrate;

b) providing a second substrate; and

c) forming a light reflective medium between the first and second substrates, the light reflective medium comprising alternating layers that include a cholesteric liquid crystal material and a polymer material,

wherein the alternating layers of the light reflective medium are oriented to reflect light of two or more intrinsic peak wavelengths in a reflection direction that is away from surface glare from the first or second substrate.

7. The method of claim 6, wherein the light reflective medium comprises separate layers including at least one layer comprising the cholesteric liquid crystal material, and at least one layer comprising the polymer material.

8. A method of making a reflective display, comprising:

a) providing a first substrate;

b) providing a second substrate;

c) forming a light reflective medium that reflects light at two or more intrinsic peak wavelengths between the first and second substrates, the light reflective medium comprising (i) a first layer comprising a first holographic polymer dispersed liquid crystal material and (ii) a second layer separate from the first layer, the second layer comprising a first cholesteric liquid crystal material,

wherein the first layer reflects light at a first intrinsic peak wavelength and the second layer reflects light at a second intrinsic peak wavelength, and

wherein the texture of the first cholesteric liquid crystal material can be changed to reflect or transmit light at the second intrinsic peak wavelength by applying voltage to the first and second substrates.

9. The method of claim 8, further comprising:

d) forming a third layer between the first and second substrates, the third layer being separate from the first and second layers and comprising one of (i) a second holographic polymer dispersed liquid crystal material that reflects light at a third intrinsic peak wavelength, and (ii) a second cholesteric liquid crystal material that reflects light at the third intrinsic peak wavelength.

10. The method of claim 9, wherein the third layer comprises the second holographic polymer dispersed liquid crystal material.

11. The method of claim 9, wherein the third layer comprises the second cholesteric liquid crystal material.

17. The reflective display of claim 10, wherein the third layer comprises the second holographic polymer dispersed liquid crystal material, and the display further comprises a voltage source that selectively applies a voltage to the first and second substrates, wherein:

when the voltage is zero, the first cholesteric liquid crystal material has a substantially planar texture and the display reflects light at the first, second and third intrinsic peak wavelengths;

when the voltage has a first value, the first cholesteric liquid crystal material has a substantially focal conic texture and the display reflects light at the first and third intrinsic peak wavelengths and transmits light at the second intrinsic peak wavelength; and

when the voltage has a second value higher than the first value, the first cholesteric liquid crystal material has a substantially homeotropic texture and the display transmits light at the first, second and third intrinsic peak wavelengths.

18. The reflective display of claim 17, wherein the voltage applied to the first and second substrates can be released from the second value to a lower value at a first rate or at a second rate;

when the voltage is released at the first rate, the texture of the first cholesteric liquid crystal material transforms from the homeotropic texture to the focal conic texture; and

when the voltage is released at the second rate, the texture of the first cholesteric liquid crystal material transforms from the homeotropic texture to the planar texture.

12. A reflective display, comprising:

a first substrate;

a second substrate; and

a light reflective medium formed between the first and second substrates, the light reflective medium comprising alternating layers that include a cholesteric liquid crystal material and a polymer material,

wherein the alternating layers of the light reflective medium are oriented to reflect light at two or more intrinsic peak wavelengths in a reflection direction that is away from surface glare from the first or second substrate.

13. A reflective display, comprising:

a first substrate;

a second substrate;

a light reflective medium that reflects light at two or more intrinsic peak wavelengths formed between the first and second substrates, the light reflective medium including;

a first layer formed between the first and second substrates, the first layer comprising a first holographic polymer dispersed liquid crystal material; and

a second layer formed between the first and second substrates and separate from the first layer, the second layer comprising a first cholesteric liquid crystal material,

wherein the first layer reflects light at a first intrinsic peak wavelength and the second layer reflects light at a second intrinsic peak wavelength, and

wherein the texture of the first cholesteric liquid crystal material can be changed to reflect or transmit light at the second intrinsic peak wavelength by applying voltage to the first and second substrates.

14. The reflective display of claim 13, further comprising a voltage source that selectively applies a voltage to the first and second substrates, wherein:

when the voltage is zero, the first cholesteric liquid crystal material has a substantially planar texture and the display reflects light at the first and second intrinsic peak wavelengths;

when the voltage has a first value, the first cholesteric liquid crystal material has a substantially focal conic texture and the display reflects light at the first intrinsic peak wavelength and transmits light at the second intrinsic peak wavelength; and

when the voltage has a second value higher than the first value, the first cholesteric liquid crystal material has a substantially homeotropic texture and the display transmits light at the first and second intrinsic peak wavelengths.

15. The reflective display of claim 14, wherein the voltage applied to the first and second substrates can be released from the second value to a lower value at a first rate or at a second rate;

when the voltage is released at the first rate, the texture of the first cholesteric liquid crystal material transforms from the homeotropic texture to the focal conic texture, and

when the voltage is released at the second rate, the texture of the first cholesteric liquid crystal material transforms from the homeotropic texture to the planar texture.

16. The reflective display of claim 13, further comprising a third layer formed between the first and second substrates, the third layer being separate from the first and second layers and comprising one of (i) a second holographic polymer dispersed liquid crystal material, and (ii) a second cholesteric liquid crystal material, wherein the third layer reflects light at a third intrinsic peak wavelength.

19. The reflective display of claim 16, wherein the third layer comprises the second holographic polymer dispersed liquid crystal material and the display further comprises:

f) a third substrate separating the first and second layers;

g) a fourth substrate separating the second and third layers;

h) a first voltage source that selectively applies a first voltage to the first and third substrates.

i) a second voltage source that selectively applies a second voltage to the third and fourth substrates; and

j) a third voltage source that selectively applies a third voltage to the second and fourth substrates,

wherein;

when the first, second and third voltages are zero, the first cholesteric liquid crystal material has a substantially planar texture and the display reflects light at the first, second and third intrinsic peak wavelengths;

when the first, second and third voltages have a first value, the first cholesteric liquid crystal material has a substantially focal conic texture and the display reflects light at the first and third intrinsic peak wavelengths and transmits light at the second intrinsic peak wavelength; and

when the first, second and third voltages have a second value higher than the first value, the first cholesteric liquid crystal material has a substantially homeotropic texture and the display transmits the first, second and third intrinsic peak wavelengths.

20. The reflective display of claim 19, wherein the second voltage can be released from the second value to a lower value at a first rate or at a second rate;

when the second voltage is released at the first rate, the texture of the first cholesteric liquid crystal material transforms from the homeotropic texture to the focal conic texture, and

when the second voltage is released at the second rate, the texture of the first cholesteric liquid crystal material transforms from the homeotropic texture to the planar texture.

21. The reflective display of claim 19, wherein the values of the first, second and third voltages applied at a given time to the first, second and third layers, respectively, can be the same or different from each other.

22. The reflective display of claim 16, wherein the third layer comprises the second cholesteric liquid crystal material.

23. The reflective display of claim 16, wherein the third layer comprises the second cholesteric liquid crystal material, and the display further comprises a voltage source that selectively applies a voltage to the first and second substrates, wherein:

when the voltage is zero, the first and second cholesteric liquid crystal materials have a substantially planar texture and the display reflects the first, second and third intrinsic peak wavelengths;

when the voltage has a first value, the first and second cholesteric liquid crystal materials have a substantially focal conic texture and the display reflects light at the first intrinsic and transmits light at the second and third intrinsic peak wavelengths; and

when the voltage has a second value higher than the first value, the first and second cholesteric liquid crystal materials have a substantially homeotropic texture and the display transmits light at the first, second and third intrinsic peak wavelengths.

24. The reflective display of claim 23, wherein the voltage applied to the first and second substrates can be released from the second value to a lower value at a first rate or at a second rate;

when the voltage is released at the first rate, the texture of the first and second cholesteric liquid crystal materials transforms from the homeotropic texture to the focal conic texture, and

when the voltage is released at the second rate, the texture of the first and second cholesteric liquid crystal materials transforms from the homeotropic texture to the planar texture.

25. The reflective display of claim 16, wherein the third layer comprises the second cholesteric liquid crystal material, and the display further comprises:

f) a third substrate separating the first and second layers;

g) a fourth substrate separating the second and third layers;

h) a first voltage source that selectively applies a first voltage to the first and third substrates;

i) a second voltage source that selectively applies a second voltage to the third and fourth substrates; and

j) a third voltage source that selectively applies a third voltage to the second and fourth substrates.

wherein;

when the first, second and third voltages are zero, the first and second cholesteric liquid crystal materials have a substantially planar texture and the display reflects light at the first, second and third intrinsic peak wavelengths;

when the first, second and third voltages have a first value, the first and second cholesteric liquid crystal materials have a substantially focal conic texture and the display reflects light at the first intrinsic peak wavelength and transmits light at the second and third intrinsic peak wavelengths; and

when the first, second and third voltages have a second value higher than the first value, the first and second cholesteric liquid crystal materials have a substantially homeotropic texture and the display transmits light at the first, second and third intrinsic peak wavelengths.

26. The reflective display of claim 25, wherein the values of the first, second and third voltages applied at a given time to the first, second and third layers, respectively, can be the same or different from each other.